Ventris Scratch Build

Discussion in 'Mid Power Rocketry (MPR)' started by Bruiser, Oct 8, 2019.

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  1. Oct 8, 2019 #1

    Bruiser

    Bruiser

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    I am starting to build my Ventris kit and am making some pretty good progress so far. I have my 1/8th ply fins cut out and "match" sanded. Same with the 1/8" ply centering rings.

    I am currently working on the baffle plates. I am turning the coupler into an ejection baffle. I never said it'd be stock; I hardly ever do that :)

    It won't be too long before I finish building my kit and will start building the rocket and I have a question...

    While looking over the instructions on the Estes website I noticed they have the builder use carpenter's glue for everything but the engine retainer. I know the kit was designed for the Estes 29mm motors and I suspect wood glue is probably fine for those motors. The question in my mind is should I use a different glue if I plan to use this rocket for my first foray into composite motors? Maybe some epoxy in select areas?

    What do you all think?

    -Bob
     
  2. Oct 8, 2019 #2

    Nytrunner

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    Wood glue will be fine for anything except the plastic parts (transition/nosecone/retainer). You may have heard the phrase here before "the paper tube will rip and delaminate before either wood glue or epoxy fails". Most use Titebond II or III
    The Ventris was built for the discontinued "Estes" Composite motors like the F50T, G40W, and G80T. The composites are punchier than BP, and it is a heavier rocket, so fly on BP with great caution and attention to rail exit speed (low-to-no wind).

    I got in the habit of using 30 minute epoxy on the plastic retainer for Pro Series II kits like this. No failures.

    Have fun! (and pay attention to recovery area....big body rockets can catch the wind and drift quite a ways from 2000' up)
     
  3. Oct 8, 2019 #3

    kuririn

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    Yup, Nyt nailed it. Wood glue for wood to wood products. Epoxy for plastic to cardboard. Specifically, many like to use JB Weld as it is a high temperature epoxy for the motor retainer. Scuff up the inside of the plastic first for a better bond.
    As mentioned the recommended motors were Estes composites, not the black powder motors:
    F26-6, F50-6, G40-7, G80-7. Since discontinued. These were rebranded Aerotech motors made for Estes.
    You might want to run sims in OR to see if the BP motors can work. Maybe longer rod or rail and 0 wind.
    Suitable 29mm composite single use motors or reloads are available from AT, you might want to run sims first.
    Laters.
     
    Last edited: Oct 8, 2019
  4. Oct 9, 2019 #4

    Bruiser

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    Thanks, I'll go with the carpenter's then.

    -Bob
     
  5. Oct 9, 2019 #5

    Bruiser

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    I finished making the plywood pieces yesterday and have started doing some assembly.

    Here is the coupler turned into the baffle. I still need to coat and glue it together. This is the first time for this design.
    Baffle Parts.jpg

    I assembled the forward and mid centering rings on the motor tube. I put a bead of glue around the inside of the tube, near where the top ring will be and inserted the motor mount in a few inches then applied another bead of glue inside the bottom of the tube for the center ring to push into place and fully inserted the tube. The glue did not really push into place like it usually does. I guess my centering rings where just a little too loose. I did not get a good glue fillet around them so I needed to come up with something.

    I came up with inserting a stir stick into a syringe. It didn't slide right in but I was able to drill out the opening in the syringe and the stir stick was a nice snug fit.
    Glue Tool.jpg


    I was a little worried that the stir stick would be too small to push the glue thru but it actually worked real well.
    Glue Fillet.jpg


    I have the first fin gluing up now. Should get on another in a bit.
    First Fin.jpg


    So here's a question. What size braided elastic should I use on this rocket? I've been transitioning from the Kevlar to 3/8" in most of my BT-60 sized rockets. Maybe 1/2" for this one?

    Thanks,
    -Bob
     
  6. Oct 9, 2019 #6

    kuririn

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  7. Oct 10, 2019 #7

    Bruiser

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    The fins are glued to the lower tube now. I am a little surprised by the weight. So far the weight is 5.3 ounces as you see it pictured. There are no fillets and the aft centering ring is not installed yet. I left the centering ring off so far so I can make sure I have a good bond at the fin/motor mount tube. I am wondering if I should use Titebond Quick and Thick as usual for the fillets or if I should use epoxy for the first time?

    Fins Lower Tube.jpg

    -Bob
     
  8. Oct 10, 2019 #8

    neil_w

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    Either way. If you want big, cosmetically beautiful fillets than epoxy is probably easier. You'll need to use an awful lot of Quick and Thick to get equivalent results (@Nytrunner has done this successfully.)

    A reasonable amount of Quick and Thick is probably sufficient for functional purposes as far as I understand.
     
  9. Oct 10, 2019 #9

    Bruiser

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    Does anyone have experience with the Estes Pro Series 1/2" shock cord? I am wondering if it's any different than the 1/2' braided elastic you can buy at WalMart or Hobby Lobby.

    Thanks,
    -Bob
     
  10. Oct 10, 2019 #10

    Nytrunner

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    Both will do the job. Wholly up to you and what you want to accomplish/learn (make sure surfaces are clean and roughed up either way):
    -Quick and thick; easy, non toxic, lighter weight, needs to build up in layers if you want a large radius fillet. Neil's finger in water technique is real handy (I do ~1 layer per inch of tube diameter). (If it's a wood/paper tube rocket, I use wood glues)
    -Epoxy; wear gloves, takes a little practice, can be messy as you get started, one application should be all you need to get your fillet radius (popsicle stick, pvc pipe, alcohol dipped finger [gloved], round implement of appropriate size, all are good for pulling the radius) (put tape outside the 'boundary' of your fillets. the slop gets pulled up with the tape after you get the fillets where you want them)
    --5 minute; strong enough for the ventris (and my L1 incidentally :rolleyes:), short working time can catch you off guard, less time to get it looking smooth. I'd mix a small batch for each fillet pair, apply with toothpick. (I don't use it for fillets anymore)
    --15/30 minute; longer cure time usually translates to more penetration of the material and a stronger bond, longer working time allows you to get it in place and pulled (It will work although I've never used it for fillets)
    --Rocketpoxy; great stuff, takes practice (real goopy to mix, rest it a little, then apply and pull). If I'm making fillets that have non wood/paper joints, I use this.

    All my PSII's have the pro series shock cord. Works well so far, I put a strip of ductape on the 6 inches nearest ejection charges to help prevent charring/burn and extend the life.
    My gut says a 1/2" elastic from other soruces will probably work as well, just be sure to protect the ends from ejection charge as mentioned above (I haven't even looked at WM or HL elastic....)
     
  11. Oct 11, 2019 #11

    Bruiser

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    It's time to glue in the coupler/baffle assembly but somebody warned me in a recent conversation about couplers wanting to "grab" before they are fully inserted. This one is four inches long so it'll need to go in 2 inches which is further than I have done before and the largest tube has been a BT-60.

    In the past I have smeared a fairly generous coat of glue on the inside of the tube and inserted the coupler while turning it slightly in one continuous motion. Will that still work or is there another technique that might work better?

    Lower with Baffle.jpg

    Thanks,
    -Bob
     
  12. Oct 11, 2019 #12

    kuririn

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    You got it. Key is one continuous motion. Sand the coupler if it is too tight.
     
  13. Oct 11, 2019 #13

    Nytrunner

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    Draw a line around the coupler where it needs to be inserted.
    Put your glue inside the body tube.
    Put your thumbnail on that line on the coupler, and insert till your thumbnail hits the the tube edge.

    One Smooth twisting motion.
     
  14. Oct 11, 2019 #14

    neil_w

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    Or if you use epoxy there's no concern. Just make sure it dries horizontally so it doesn't drift!!!
     
  15. Oct 12, 2019 #15

    Bruiser

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    The insertion of the coupler into the lower tube went very smoothly. I also did the fillets with two passes of Titebond Thick and Final.

    I'd like to glue on the upper body tube but I'm stuck at a decision point due to the Kevlar. You can see the eye hook in the ejection baffle. I have some 250 pound Kevlar string that I normal tie into a loop. So then I take one end and stick an inch or so thru the eye then I take the other end and stick it thru the loop and pull it tight. I don't know what to call it but I also do the same type of thing at the top with a split ring. I put the end thru the split ring then work it around the ring and pull the ring until it makes sort of a knot. FYI, the split ring is where I transition to the braided elastic part of the harness. I've been doing it this way on all my BT-60 based rockets. I don't know if using the 250 pound Kevlar in the Ventris will be strong enough. I am thinking of going up to the 380 pound Kevlar.

    -Bob
     
  16. Oct 12, 2019 #16

    Nytrunner

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    I have doubled 100 lb in my ventris booster, so effectively 200lb (assuming its 100. It's that thin stuff from Apogee's BT-60 ebay kit)
    Pretty sure the 250 is fine for your application.


    As described in the thread below, I took a length of it, glued it to the motor mount, and ended it before the end of the tube where the elastic tied on.
    https://www.rocketryforum.com/threa...ctice-psii-trainer-fleet.140897/#post-1701364
     
  17. Oct 15, 2019 #17

    Bruiser

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    FYI, I went and bought a package of 1/2" non-rolling elastic at Walmart and compared it to the 1/2 Pro Series elastic that was :) in a Majestic kit I had. Testing found that the Pro Series elastic was much stouter than the Walmart elastic. I'd say it took almost twice the force to stretch it the same distance as the Dritz brand from Walmart.

    -Bob
     
  18. Oct 15, 2019 #18

    neil_w

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    That is knitted elastic, you want *braided*, which is the stronger stuff. Note how differently they behave when stretched.
     
  19. Oct 15, 2019 #19

    kuririn

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    Or you can go with 1/8 - 1/4" round elastic. Very strong, some manufacturers supply them with their MPR kits.
    Also known as a bungee cord.:D
     
  20. Oct 15, 2019 #20

    Bruiser

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    I am doing something a little different with the payload area of this rocket. Instead of gluing the transition to the payload tube and the payload tube to the nose cone I want to attach them in a removable way. I am thinking the plastic rivets. My reason for doing so is that at some point in the future I want to try dual deploy with this rocket.

    I am thinking maybe three rivets at each joint or should I do four? I've been to one local automotive store and didn't see any rivets there that fit the bill. Still have another to check out. I am thinking that once I make the holes thru the body tube I can harden the area with some CA glue to strengthen it.

    I applied cwf to the payload tube and have it sanded down. The payload tube fit to both the nose cone and transition was pretty loose. I coated the inside of the payload tube ends with CA like I usually do and the nosecone is snug now but the transition is not. I'm not sure what to do about that as past builds have always been snug and needed to be sanded after I CA'd the body tube.

    -Bob
     
  21. Oct 15, 2019 #21

    Charles_McG

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    I use three, but you'll have a hard time getting the part I use.

    Tomahawk-12 payload.jpg

    Two of the 3 are visible in this Ventris-derived Tomahawk-12.
    I used parts from the pressure relief valve from a [now defunct] plastic one-way keg vendor. The little domes have side hooks on 2 sides. I use a little screwdriver to pry them out. They have a hole through, so act as rivet and vent port.

    I think the dome shape created an artificially high barometric altitude reading with an error proportional to airspeed. So whatever you use, watch its profile if it also vents.

    I lost this one on its first flight - tracker died and I flew anyway. Discovered that mylar streamer visible tracking that works at 2000' doesn't at 4000'.

    Just started painting the replacement last night. I ground the dome to a flatter profile, hoping to get less Bernoulli this time.
     
  22. Oct 15, 2019 #22

    Nytrunner

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  23. Oct 17, 2019 #23

    Bruiser

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    The Ventris is coming along. A light sanding should be all she needs before the first color goes on.

    Lower in Primer.jpg

    -Bob
     
  24. Oct 17, 2019 #24

    Bruiser

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    As for color, I have been thinking about changing things up a little. The "normal" color scheme (as on the face card) is on the left. I am thinking of painting the nose cone, payload bay and transition blue which is on the right.
    Two Ventris.jpg

    What do you all think? Does it look bad? Would changing the color be sacrilege?

    -Bob
     
    Last edited: Oct 17, 2019
  25. Oct 17, 2019 #25

    kuririn

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    Nothing is set in stone. Do whatever you feel like.
    Case in point: Nytrunner's Phoe…. I mean Hot Bird.
     
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  26. Oct 17, 2019 #26

    Bruiser

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    I had a crazy idea. What if the nose was red and the tail was blue... I think I like it!

    Triple Ventris.jpg

    -Bob
     
  27. Oct 17, 2019 #27

    neil_w

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    The answer to this is almost always a resounding "no".

    The case that really put this to the test was the recent Saturn V drag race that had... well, let's just say a number of "non-traditional" paint schemes (dunno if I can find that picture, it's a hoot.) To me, if any rocket had a "sacred" paint scheme, it would be that one. But it was fine. Some scale nerds might get offended (which would be *their* problem), but otherwise do whatever you want. Certainly, for a sport rocket like the Ventris you shouldn't even think twice.
     
  28. Oct 17, 2019 #28

    Hooked On Rockets

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  29. Oct 17, 2019 #29

    Bruiser

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    I've been following your build. I'm interested in how cutting stencils out with the cricut works for you. Are you going to use the letters or are you going to make a paint mask and paint the letters on?

    I do enough scale builds that I like to keep my sport rocket schemes pretty simple. Did you see my gooney build from a Baby Bertha :)
    Patriot Gooney Paint w Lug Small.jpg

    Anyway, I don't know if I am going to put "VENTRIS" on this rocket or not. I'm thinking it over. No decals actual came with the kit but they were available for an extra cost I guess. Mark at Sticker Shock also had some vinyl for them and the word "VENTRIS" was included. After I put the color on I'll decided if it needs anything more.

    -Bob
     
    Last edited: Oct 17, 2019
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  30. Oct 18, 2019 #30

    Bruiser

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    I sprayed the white today (Rustoleum Gloss White) and had a few problems. It was all going well then two short pieces of hair (1/4" or so) settled on the paint as soon as I sprayed the flow coat. I got out my x-acto knife and lifted the hairs off. Of course that smeared the paint a little so I sprayed on some more white. Looked good for a few seconds but then I got some bubbles in the paint followed by two small runs. I'll wait for it to dry then I'll sand out the problem areas and spray another coat. That should take care of it, at least I hope so :)

    -Bob
     

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